Precision voltage regulator

ABSTRACT

A voltage regulator providing a very stable output voltage with respect to time, temperature, and load, by supplying a stable, constant current to a reference diode. The regulator has an operational amplifier, and a plurality of zener diodes coupled thereto.

lnventor Appl. No.

Filed Patented Assignee Samuel A. Miller China Lake, Calif.

Feb. 1, 1971 Jan. 11, 1972 v The United States of America as represented by the Secretary of the Navy PRECISION VOLTAGE REGULATOR [50] Field of Search 323/2, 9, 17, 40, 67, 75 F, 22 2; 330/146 [56] Relerences Cited UNITED STATES PATENTS 3,387,206 6/1968 Sampson 323/40 UX 3,538,427 11/1970 Oltendorf 323/40 X Primary Examiner-Gerald Goldberg Attorneys-R. S. Sciascia, Roy Miller and Robert W. Adams 8 Claims, 2 Drawing Figs.

...................................................... A voltage regulator roviding a very stable out- 323/22 Z, 323/40, 323/7 F m voltage with respect to time, temperature, and load, by Int. Cl G05f 1/46 Supplying a b consmm current to a referencc diode The regulator has an operational amplifier, and a plurality of zener diodes coupled thereto.

E l 2 l4 PATEMEDJAM 1 m2 3.634.751

INVENTOR.

SAMUEL A. MILLER Y ROY MILLER ROBERT W. ADAMS ATTORNEYS.

PRECISION VOLTAGE REGULATOR STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION In the field of electronics, a need exists for a device which will provide a precision reference voltage but does not itself require a regulated voltage supply. Most prior devices which provided a precision reference voltage require a voltage supply having at least good regulation.

SUMMARY OF THE INVENTION The present invention is a precision voltage regulator having at least an operational amplifier and a plurality of constant resistive means and variable resistive means. In the preferred embodiment the constant resistive means are resistors, and the variable resistive means are zener diodes. The output of the operational amplifier is coupled to both its negative and positive inputs such that the voltage appearing across the terminal of one of the temperature compensated zener diodes is stable with respect to time, temperature, and load. Additionally, the input bias current and input offset current changes of the operational amplifier are much less critical in the present invention than in prior devices.

BRIEF DESCRIPTION OF THE DRAWINGS F IG. 1 is a schematic diagram of a preferred embodiment of the invention which provides a positive reference voltage; and

FIG. 2 is a schematic diagram of a preferred embodiment of the invention which provides a negative reference voltage.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 wherein the preferred embodiment of the present invention for generating a positive precision reference voltage comprises a supply voltage 10, an operational amplifier 12, zener diodes l6 and 26, resistors and 24, and reference voltage output 28. The output of operational amplifier 12 is coupled to the diode 16 of diode l6-resister 24 voltage divider, the junction of which is coupled to the negative input 18, the inverting terminal, of amplifier 12. The side of resistor 24 opposite the junction is coupled to ground. The amplifier output is also coupled to resistor 20 of resistor 20-diode 26 voltage divider, the junction of which is coupled to the positive input 22, the noninverting terminal, of amplifier 12. The anode end of diode 26 is coupled to ground. The circuit provides a highly regulated voltage across zener diode 26 at output 28.

The operation of the positive voltage-generating circuit is as follows: The purpose of the circuit is to retain the current through diode 26 at a constant value, thereby producing a constant precision reference voltage at output 28. Since the input impedance of the high gain, differential, DC operational amplifier 12 is quite high, and therefore, draws approximately zero current, the current through diode 26 can be measured by the voltage drop across resistor 20. Similarly, the current passing through diode 16 can be measured by the voltage drop across resistor 24. If circumstances occur which cause the current through diode 26 to become smaller, that reduced current will be reflected by a reduction in the voltage at junction 14. The voltage at positive input 22 will change very little.

A decrease in the voltage at junction 14 results in an almost equal decrease in the voltageat negative input 18 since diode 16 tends to maintain a near constant voltage drop between junction 14 and terminal 18. Therefore, the voltage change at inverting terminal 18 will be much greater than the voltage change at noninverting terminal 22. As a result, the voltage at junction 14 will be driven in a positive direction; thereby, causing the current through diode 26 to increase, restoring it to its original value.

2 The sensitivity of the precision reference voltage appearing at output 28 to the various components of the circuit is as follows:

While applicant does not wish to be limited to any particular set of circuit constants, the following constants have proven to be useful in generating a positive reference voltage.

Symbols Description Value V Voltage at noninverting terminal 22 6.2 volts V Voltage across diode 16 6.2 volts R, Dynamic resistance of diode 26 I0 ohms R, Dynamic resistance of diode l6 10 ohms R, Resistance of resistor 20 800 ohms R Resistance of resistor 24 800 ohms Referring to FIG. 2 wherein the preferred embodiment of the present invention for providing a negative reference voltage comprises a supply voltage 10, an operational amplifier 12, zener diodes 16 and 26, resistors 20 and 24, and reference voltage output 28. The operation of the negative voltage generating circuit is similar to that described above, and therefore, will not be repeated. The circuit of FIG. 2 is the circuit of FIG. 1 modified to provide a negative reference voltage.

While applicant does not wish to be limited to any particular set of circuit constants, the following constants has proven to be useful for providing a negative reference voltage.

Symbols Component Type or Value 10 Supply voltage 15-40 volts 12 Operational amplifier LM I0] 16 Zener diode lN829A 20 Resistor 820 ohm, 3 watt 24 Resistor 820 ohm, 3 watt 26 Zener diode lN829A 28 Reference voltage output 6.2 volts Although standard zener diodes may be used in the present invention, improved results can be obtained by using temperature compensated zener diodes as diodes 16 and 26.

Note that reference voltage output 28 is insensitive to supply voltage 10, thereby, eliminating the necessity of providing a well regulated supply voltage to the present invention. Therefore, any supply voltage which provides an output within a large range of possible values may be utilized in the present invention.

What is claimed is:

l. A voltage regulator providing a precision reference voltage output, comprising:

an operational amplifier providing an output;

a supply voltage coupled to said operational amplifier; and

a plurality of variable resistive means for providing variable electrical resistance. and a plurality of constant resistive means for providing constant electrical resistance, coupled to said operational amplifier such that said variable resistive means and said constant resistive means are arranged in a plurality of voltage divider networks;

wherein the voltage across at least one of said variable resistive means is a precision reference voltage.

2. The regulator of claim 1, wherein a first variable resistive means is coupled between the output and a first input of said operational amplifier, and a first constant resistive means is coupled between the output and a second input of said operational amplifier.

3. The regulator of claim 2, wherein a second variable resistive means and a second constant resistive means are coupled in combination between said first input and said second input of said operational amplifier.

4. The regulator of claim 3, wherein said first input is the inverting terminal of said amplifier, and said second input is the noninverting terminal of said amplifier.

5. The regulator of claim 4, wherein said first variable resistive means and said second variable resistive means are zener diodes, and said first constant resistive means and said second constant resistive means are resistors.

6. The regulator of claim 5 wherein the resistor end of said combination of said variable and said constant resistive means is coupled to the inverting terminal of said operational amplifier, and the diode end of said combination is coupled to the noninverting terminal of said operational amplifier.

7. The regulator of claim 6 wherein said zener diodes are temperature compensated zener diodes.

8. The regulator of claim 7 wherein the voltage across said second variable resistive means is said precision reference voltage output. 

1. A voltage regulator providing a precision reference voltage output, comprising: an operational amplifier providing an output; a supply voltage coupled to said operational amplifier; and a plurality of variable resistive means for providing Variable electrical resistance, and a plurality of constant resistive means for providing constant electrical resistance, coupled to said operational amplifier such that said variable resistive means and said constant resistive means are arranged in a plurality of voltage divider networks; wherein the voltage across at least one of said variable resistive means is a precision reference voltage.
 2. The regulator of claim 1, wherein a first variable resistive means is coupled between the output and a first input of said operational amplifier, and a first constant resistive means is coupled between the output and a second input of said operational amplifier.
 3. The regulator of claim 2, wherein a second variable resistive means and a second constant resistive means are coupled in combination between said first input and said second input of said operational amplifier.
 4. The regulator of claim 3, wherein said first input is the inverting terminal of said amplifier, and said second input is the noninverting terminal of said amplifier.
 5. The regulator of claim 4, wherein said first variable resistive means and said second variable resistive means are zener diodes, and said first constant resistive means and said second constant resistive means are resistors.
 6. The regulator of claim 5 wherein the resistor end of said combination of said variable and said constant resistive means is coupled to the inverting terminal of said operational amplifier, and the diode end of said combination is coupled to the noninverting terminal of said operational amplifier.
 7. The regulator of claim 6 wherein said zener diodes are temperature compensated zener diodes.
 8. The regulator of claim 7 wherein the voltage across said second variable resistive means is said precision reference voltage output. 